You notice that the computer is unusually slow, crashes, or stops responding frequently.

You cannot start your virus scanner or some system tools, including Task Manager.

You cannot open certain webpages. In particular, you cannot open security-related webpages such as the Windows Update website.

You notice that your web browser's home page has changed unexpectedly, and you cannot restore the home page.

You receive constant and unexpected pop-up windows.

These symptoms may indicate that your computer is infected with malware. However, the same problems might also point to hardware or software issues that have nothing to do with malware. Because it is difficult to determine the reasons for your computer's strange behavior, we suggest that you review the information in this article to determine whether malware is causing the issue. Then, you can use the recommended tools and resources to remove the malware.

Microsoft Windows Update

Run Windows Update to obtain the latest updates for Microsoft software, and this includes security updates that are released on the second Tuesday of each month. For more information, visit the Microsoft Update website:

Microsoft Security Essentials

Microsoft Security Essentials is free and can help protect your home or your small business system from viruses, spyware, and other malware. For more information, visit the following Microsoft webpage:

Microsoft Safety Scanner

If you think your computer is infected, we recommend that you run the Microsoft Safety Scanner. The scan is free and will detect and remove many of the issues that customers frequently contact us about. To run the Microsoft Safety Scanner, visit the following Microsoft webpage:

Microsoft Windows Security Center

Run the Windows Security Center to check the status of several security essentials on your computer. To do this, click Start, type Check security status, and then click Check security status.
For more information about the Windows Security Center, visit the following Microsoft webpage:

Windows firewall

The Windows firewall is included in most supported versions of Microsoft Windows. The Windows firewall can help protect your computer from malicious users. For more information, visit the following Microsoft webpages:

Microsoft Malware Protection Center

The Malware Protection Center (MMPC) provides information about protection against viruses, spyware, and other potentially unwanted software. The MMPC also supplies the core anti-malware technology (This includes the scanning engine and the malware definition updates) for the following:

Microsoft Malware Protection Center Encyclopedia

Microsoft Virus and Security Solution Center

The Microsoft Virus and Security Solution Center provides free tools that can help detect and remove viruses. These tools can also strengthen defenses to help secure your computer against viruses and other security threats.

Microsoft Safety & Security Center

The Microsoft Safety & Security Center has information about Security scanners, tools, and safety guidelines for your computer, laptop, or mobile device.
For more information, visit the following Microsoft webpage:

Security Troubleshooting and Support

The Security Troubleshooting and Support page has information about free tools that can help detect and remove viruses. The support page also contains information about how to strengthen defenses to help secure your computer against viruses and against other security threats. For more information, visit the following Microsoft webpage:

What you can do to help prevent your computer from becoming infected

There is no method that can guarantee that your computer will be immune from malware. However, there are steps that you can take to lessen the risks. For more information, visit the following Microsoft webpage:

Information about fake virus alerts and rogue security software

Rogue security software, also known as "scareware," is software that seems to be useful from a security perspective. However, this rogue security software provides limited or no security, generates incorrect or misleading alerts, or tries to lure users into participating in fraudulent transactions. For more information, visit the following Microsoft webpage: